Art of grinding hobs



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1 2 Feb 157 9 7 J. EDGAR ART OF GRINDING HOBS Filed June 22 1925 5 Sheets-Sheet v2 w .w m

1927. Feb 15 J. EDGAR ART QF GRINDING Hos Filed June 22, 1925 5 Sheets-Sheet 3 Z Lm f l- Feb. y15, 1927. 1,617,798

J. EDGAR ART OF GRINDING HOBS Filed June 22 1925 s sheets-sheet 4 7 gwuaM/tofa:

d Eff dom@ dgar f l 617 798 Feb. 15, 1927. J. EDGAR- r y ART OF GRINDING HOBS Filed June 22 1925 5 Sheets-Sheet 5 i Jaim@ idg@ 32,1?, M

Panarea Feb. 15,1921.

UNITED STATES PATENT OFFICE.

JOHN EDGAR, OF ROCKFORD, ILLINOIS, ASSIGNOR v'.lO BARBER-COLMAN COMPANY, OF

ROCKFORD, ILLINOIS, A CORPORATION ART OF GRINDING HOBS.

Original application led .Tune 28, 1916, Serial No. 106,339. Divided and this 0F ILLINOIS.

application led June 22,

1925. Serial N0. 38,645.

give them sion ot' application Serial No. 106,339, and

claims said process.

A hob has one or more spiral series of 'relieved cutting teeth, the cutting faces of the teeth ybeing defined by gashes which may be either straight (i. e., parallel with the axis of the hob) or spiral. In order that the hob shall have relatively long life, the eircumferential length of the teeth is' made as great as possible, which means that the gashes are relatively narrowmuch narrower, proportionately, than in the case of -a tap, for instance. Because of the length of the teeth, there is considerable diierence between the height of a tooth at its front end and its height at its rear end, which fact necessitates a relatively long relieving stroke and an abrupt return stroke. Moreover, because of the narrowness of the gashes it is iinpracticable to grind thegtwo opposite sides of a tooth space at the same time. Be-

iore finishing one such tooth space the grinding wheel would engage the next tooth space.

In order to avoid rotating the grinding element at ari objectionably high speed and to prevent excessive wear on the grinding element, it is desirable to use an abrasive Wheel of relatively large diameter; and in order to obtain clearance between the Wheel and ea'ch succeeding tooth, it is desirable to mount the wheel so that its periphery may be employed in grinding.

The machine herein disclosed is specially adapted to fulfil the requirements peculiar to the grinding ot hobs, straight-gashed as well as spiral-gashed, and to produce accurate work at a relatively fast rate and with Ia minimum of interruption for dressing the grinding element.

it is necessary to In the accompanying drawings, Figure 1 1s a top plan view'of one form of hob grinding machine which may be employed in carrying out my improved process.

Fig. 1f* is a fragmental sectional `View of the tailstock of the machine.

Fig. 1b illustrates the position of the grinding wheel 'with relation to the hob.`

F ig. 2 is a sectional view of the connection between the hob slide and the feed screw for moving said slide, the View being taken in the plane of dotted line 2-2 of Fig. 5.

Fig. 3 is a fragmental side elevation of the machine.

Fig. 4 is a section taken in the plane of dotted line 4 of Fig.

Fig. 5 is a section taken in the plane of dotted line 5 of Fig. 1.

Fig. 5 is a view of a carrying head.

Fig. Fig. 1.A I

Fig. 7 is a horizontal central sectional view of the hob-supporting means.

Fig. 8 is a view looking from the left-hand end of Fig. 3. f

Fig. 9 is a` sectional view of the means for rotating the hol.

Fig. 10 is a view of the means for indexing a.-pluralthread hob. Fig. 11 is a section on dotted line 11 of Fig.

Fig. 12 is a section Fig. 4.

Fig. 13 is aseetion on dotted line 13 of Fig.4. i F Fig 14 is a section on dotted line 14 of Fig. 15 is a section Fig. 5.

Referring to the top plan view entitled Fig. 1: A indicates a hob and B a grinding wheel. In operation, the grinding wheel B is rotated at high speed. The hob A is slowly rotated in the opposite direction and is also given a movement of translation past the grinding wheel, the rotation and movement of translation of the hob bein so proportioned to each other that one si e of the thread (or more accuratel speaking, the spiral series .of relieved teeth) of the hob is presented to thegrinding wheel. After the hob has been fed past the grinding clamp for the wheelon dotted line 12 of on dotted line 15 of Bussum 6 is a sectionon dotted line 6 of i wheel, the hob is returned to initial position and adjusted with relation to the grinding wheel so that the latter shall be able to remove more material. The hob is then rotated and fed past the grinding wheel as before. These operations are repeated until one side of the thread of the hob has been completely ground. The head that carries the grinding wheel is then reversed so as to. place the grinding wheel in position to grind the other side ofthe thread of the hob. The hob is then fed/past the grinding wheel the desired number of times until the last mentioned side of the thread has been properly ground.

A slide 1, upon which the hob is supported, is mounted upon two guides 2 and 3 (Fig. 5) formed upon the bed of the machine. Upon the slide'l is a headstock 4 and a tailstock 5, the latter being adjustable toward and away from the headstock upon a guide 6. The tailstock is secured to the slide 1 in adjusted position by means of a boltA 7 (Fig. 1a) extending through the tailstock, the head of said bolt lying within a T-slot 8 in the slide. A spindle 9 (Figs. 1, 3 and 7) is rotatably supported in the headstock 4 and is held against longitudinal movement in said headstock by means of a flange 10 and a collar 11. The spindle 9 is made tubular to permit of inserting and removing the support or arbor 12 that carries the hob. -The arbor 12 has a tapered portion adapted to be driven into a correspondinglytapered socket in the end of the spindle 9.

The spindle being tubular, as shown in Figs. 7 and 9, a rod may be inserted into the other. end of the spindle for the purpose of driving out the arbor 12 when necessary. The hob is secured upon the arbor between an annular shoulder 13 and a nut 14, and is further' held against rotation with relation to the arbor by lmeans of a key 15. The end of the arbor opposite to the tapered end is provided with a center 16 arranged to be rotatably supported by a sleeve 17 carried by the tailstock 5. Said sleeve is held against rotation by means of a key 18 and is arranged to be moved into and out of operative relation to the center 16 by means of a screw 19 having an operating hand wheel 20. Clamp members 17a (Fig. 1a) and a screw` 17b provide means for securely locking the sleeve 17 against movement.

The means for rotating the spindle 9 comprises a sleeve 21 (Fig. 9) rotatably mounted in bearings 22 and 23 in the 'supporting framework of the machine. The spindle 9 is slidable longitudinally of the sleeve 21, but is -caused to rotate with the sleeve by means of a spline 24 (Fig. 9) connected to the sleeve and lying within a key- Way 25 in the spindle. By means to be later described, the Asleeve 21 is adjustably connected to a gear wheel 26 that meshes with the bearing 33 a pinion 27 (Fig. 1) fixed on the drive shaft 28. On said shaft is secured a stepped pul-A ley 29. Said pulley is driven from a reversible countershaft (not shown) or other 'suitable source of power.

The. means for feeding the slide l comprises a feed screw 3() (Figs. 4 and 5) suported in a bearing 31 in the machine frame.

igid with the slide 1 are two downwardly extending lugs 32 (Figs. 2 and 5). A bearing 33 lies between these lugs and has flanges 34 to cause the lugs and bearing to travel together. Rotatably mounted in the bearing 33 is a nut 35, said nut being held against cndwise movement with relation to the bearing. 33 by means of a shoulder 3&5 and a nut 37. The nut 35 is threaded upon a nut 38 ou the feed screw 30. The nut 38 is prevented from rotating with relation to by means of an arm 39 which is rigid with said nut, said arm having an opening through which a pin 40 is slidable (see Fig. 4), said pin being fixed in the bearing 33 and extending longitudinally of the feed screw 30. )Vlien the feed screw 30 is rotated, the nut 38 will be caused to move longitudinally of said feed screw, the nut 38 carrying with it the nut 35, the bearing 33 and the lugs 32, and thus imparting movement to the slide 1.

In order that the slide 1 shall be adjustable with relation to the nut 38 I provide a shaft 41 rotatably supported in the slide 1 and having upon its lower end spiral gear teeth 42 meshing with similar teeth 43 formed upon the nut 35. The upper end of the shaft 41 is squared to receive a crank. Fixed to the shaft 41 is a micrometer dial 44 arranged to coact with a zero mark on the adjacent portion of the slide. After the wheel AB has made a cut and the slide 1 has been returned, the slide may be adjusted by means of the shaft 41 to permit the grinding wheel Bto make another cut on the same side of the thread of the hob.

The feed screw 30 is arranged to be rotated by power means for advancing the hob with relation to the grinding wheel and is also arranged to be rotated by lnanually actuated means for the purpose of returning the slide 1 to initial position; said manually actuated means comprises a shaft 45 (Figs. 1, 3 and 4), said shaft being connected to the feed screw 30 vby means of spiral gears 46 and the outer end of said shaft being squared to receive a crank.

The power means for rotating the feed screw 30 comprises a clutch shaft 47 4) alined with and supporting one end of the feed screw 30 and having a clutch face 48 arranged to be engaged by a clutch member 49 which is slidable longitudinally of the feed screw 30. The feed screw 30 and the clutch` member are caused to rotate together by means of a key 50 (Fig. 11). The

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' secured to the disk 59 by clutch member 49 is arranged to be slid longitudinally of the feed screw 30 by means of a fork 51 engaging said clutch member and fixed upon a rock shaft 52. Upon the outer end of the rock shaft 52 is fixed' a hand crank 53 (Fig. 3). After the clutch member 49 has been disengaged from the clutch shaft 47, the shaft 45 may be rotated to adjust the slide 1 .to place the-hob in approximately operative relationto the grinding wheel. Fixed to the clutch shaft 47 is a change-gear 54 (Figs. 4 and 8) meshing with a. change-gear 55; 'the latter gear is rigid with a change-gear that meshes with a change-gear 56; the change-gear 56 isI rigid with a gear 57 that meshes with a gear 58 which is rigid with the gear 26; the latter, it will be remembered, meshes with a pinion 27 on the drive shaft 28.

A hob may have one or a plurality of threads. After one thread of a multipleJ thread hob has been ground, it is necessary to turn the hob tobring another thread into position to be round. yFor this purpose the 4 spindle 9 is adjustably connected to the gear wheel 26. Rigid with the sleeve 21 is a flange or disk 59. A ring 60 is adjustably means of bolts 61 extending through the disk 59 and having heads that lie Within circular under-cut slots 62 in the ring 60. The ring 60 is adjustably secured to the gear wheel 26 by similar clamp bolts 63. For setting the ring 60 with relation to the gear wheel 26 there is provided a' spring-pressed index pin 64 carried by the lgear wheel 26 and arranged to enter any one of a number of openings in the ring 60. When one thread of a double-thread hob has been ground, the

clam bolts 63 are loosened, the index pin 64 dliawn back and the ring 60 turned through one-half of a revolution, thus bringing an opening 65 into register with the index pin 64, which latter is then permitted to sprino into said opening. In the case of a trip e-thread hob the operator would turn the ring 60 with relation to the gear wheel 26 through one-third of a. revolution, thus bringing an opening 65 into register with the index pin 64. For thus turning the ring 60, a bar (not shown) would be inserted in openings 21 (Fig. 9) in a collar on the sleeve 21. Any desired number or arrangement of openings 65 may be provided to take care of hobs having various numbers of threads. In order that the spindle 9 may be adjusted for hobs having a number of threads not provided for by the spacing of the openings 65, the disk 59 and the ring 60 are adjust-ably connected together as hereinbefore stated. A graduated ring 66 is rotatably mounted upon the periphery of the disk 59 andv is secured thereto in adjusted position by means of a clamp bolt 67. On the ring 60 is a Vernier cla-mp bolts 61 are then 68. Normally the zero line on the ring 66 is opposite the zero line of the Vernier 68. After one thread of a hob having such special numberof threads has been ground, the hob is turned to bring the next thread into position to be acted upon bythe wheel B by loosening the clamp bolt 61 and turning the disk 59 with reference to the Vernier 68 through an arc of the necessary length. The tightened, the bolt 67 slackened, the ring 66 returned to zero position and the bolts 67 afrain tightened. When the next thread is to zbe ground, the flange 59 is again turned with reference to the Vernier 68 through the same angular distance as before. t

The adjustable connection between the flange 59 and the ring 60 affords means for conveniently setting the hob with relation to the relieving cam 71 so that as thethob `rotates the grinding wheel shall be moved outwardly in time to begin operation on each succeeding tooth.

The grinding wheel 69 (Figs. 1 and 5) which is reciprocable at right angles to the direction of movement of theslide 1. As shown in Fig. 5, the teeth of the hob A are relieved with a uniform clearance. As a tooth revolves past the wheel B, the slide 69 is the slide 1 to maintain the Wheel in proper relation to the tooth. As soon as the tooth has passed the wheel the slide 69 is given a quick outward movement to place the wheel in position to grind thev tooth. The means for thus reciprocating the slide 69 comprises a shaft 70 (Figs. 1, 3 and 5) carryin against a lock 72 upon the slide 6 9. As

shown in Fig. 14, the shaft 7 0 is made in two I sections connected by the one-Way clutch 73 shown in Fig. 13, in order that the cani 7l shall not interfere with reverse movementof the rest of the machine when it is desirable to turn the drive justing the relation of the hob to the grinding wheel. The shaft 7 0 is driven from the drive shaft 28 through change gears 74, 75 and 76 (Fig. 8).

The s ide 69 is moved away from the hob by means of a coiled compression spring 7 7 (Fig. 5) which bears at one` end against a stationary post 78 and is adjustably connected at its other end to a lug 79 on the slide 69. A rod 80 fixed to the ost 78 and extending freely through the ug 79 carries' a nut 81 which may be turned up against the lug 79 for the purpose of forcing the slide 69 away from the cam 71 when to besubstituted.

U-pon the slide 69 is mounted a slide 82 for movement parallel with the direction of movement of the slide 69. en the inachine is running the slide 82 is stationary with' relation to the slide 69, but means is next succeedingl l a cam 71 arranged to operateshaft 28 backward in ad- B is carried by a slide another cam is against the lug 84 and at its other provided whereby the slide 82 may be moved toward and away from the hob when the machine is being adjusted. Referring to Fig. 5: A bar 83 is fixed to a lug 84 on the slide 69. On the bar 83 is slidably and rotatably mounted an adjusting screw 85 having holes 85a to receive an implement for turning the screw. The screw 85 is slidably and rotatably supported in a guide 86 on the slide 69. A coiled compression spring 87 surrounding the bar 83 bears at one eng en against a portion of the screw 85. The spring 87 is restrained by a hand lever 88 (Fig. 1) which is pivoted to the outer end of the bar 83, said Ahand lever having avcam portion 89 that bears against a washer which in turn lies in Contact with the screw 85. A detent 88a yieldingly locks the handle 88 against movement.

The slide 82 is fixed to the screw 85 by the means shown in Figs. 5 and 6. 90 is a nut rigidly secured to the slide 82 and engaging the screw 85. In order that the nut 90 may be tightly clamped to the screw 85, said nut is split at one side (as at 91) and is arranged to be contracted into clamping engagement with thescrew by means of a screw 92.

The grinding wheel spindle is carried by a frame 93 (Fig. 15) provided with trunnions 94 which are mounted for oscillation in a bearing 95 on the slide 82 and in a bushing 96 carried by a portion 97 of the slide 82.` It will be observed that the bearing 95 and portion 97 of the slide together constitute a tool post in which the tool-carrying frame 93 is pivoted upon an axis a (Figs. 1b and 15) intersecting the axis b of the hob at a right angle. When grinding the hob the Vpoint of intersection c of the pitch line dv and the line of Contact of the hob and the grinding Wheel is in the axis a of the trunnions 94. The frame 93lis arranged to be held against swinging movement by 'means of a Screw 98 engaging a threaded opening 99 inl said frame and adapted to extend through either of two diametrically opposite curved slots 100 in the slide portion 97. When dressing a grinding wheel that is to be used in Grinding the teeth of a spirally gashed ho the frame 93 should be secured in the horizontal plane of the spindle 9, and for thispurpose I provide a positioning pin 101 adapted to be inserted into either one of two openings 102 provided at diametrically opposite points in the portion 97'. The pin 101 is adapted to enter a hole 103 in the frame 93. The pin 101 is used onlyin setting the frame 93 preparatory todressing the grinding Wheel, and at other` times is withdrawn from the openings 102 and 103.

For setting the frame 93 at an an le corresponding to the angle of the threa of the hob= I provide a protractor ring 104 (Figs.

1, 5 and 15) rotatably'mounted upon the bushing 96 and arranged to be clamped to the portion 97 by means of bolts 105 extending' through the portion 97 and having heads lying in an annular T'-slot 106 in the protract'or ring. points on the protractor ring are formed notches 107 to receive a spring-pressed detent pin 108 carried by the frame 93. For withdrawing the pin 108 from engagement with a notch. 107, there is'provided a pinion 109 arranged to engage rack teeth formed on the pin 108. The upper end of the pinion 109 is adapted to be engaged by a key 110.

The protractor ring 104 is provided with graduations as shown in Fig. 1, and the portionl 97 is provided wtli a cooperating zero mark.

The grinding wheel spindle is carried by a power head 111 which is mounted in a clamp on the frame 93. The construction of this clamp will be apparent from Fig. 5a. The jaw 112 of the clamp is relatively stational-y, while the jaw 113 is arranged to be drawn toward the jaw 112 by means of a bolt 114 and nut 115 so as to clamp the head 111 rigidly to the frame 93. The clamp jaw 113 is loosely secured to the frame 93 by means of two screws 116 (Fig. 15). After the nut A has been lcooiened, the head 111 may be slid back and fort-h with relation to t-he frame v93 by operatng nuts 117 on a screw stud 118'fixed to the frame 93, said nuts lying at opposite sides of a lug 119 on the head 111.

The grinding wheel B is removably secured in any usual or suitable way to a spindle 120 (Fig. 15), the axis of which intersects the axs of the frame 9.3. Said spindlehas a tapered portion which lies within a correspondingly-tapered bushing 121 in the head 111. the spindle being urged forward against said bushng by means of a coiled spring 122. Fixed to the spindle 120 is a gear wheel 123 that meshes with a At diametrically opposite n gear wheel 124 on a haft125 arranged paralli-l to the spindle and carried by the head 111. Rigid with the shaft 125 is a bevel gear wheel 126 that meshes wlth crown gear teeth formed upon one side of a fianged driving pulley 127, said pulley being rotatably mounted upon a stud 128 fixed to the head 111. Thepulley 127 receives a belt 129 extending rom a counter-shaft or other suitable source of power.

' While the sequence of operations in makf ing the several adjustments maybe varied. the operation of grinding a single-thread hob may be described, in general as follows-1 Thehandle 88 (Fig. 1) is operatedto` allow the spring 87 (Fig. 5) to move the slide 82 outwardly. The frame 93 is adjusted, with the aid of the protractor ring 104, to the pro er inclination with reference to the ang e of the thread of the hob (see Fig. 3),

the frame QS-being secured in adjusted position by means of the screw 98. The tailstock 5 is'slid away from the headstock 4. The arbor 12 is inerted into the tapered end ofbtlie spindle 9. The hob is placed on said ai' end of the sleeve 17 against the center 16. The nut on the bolt 7 is tightened -up to clamp the tailstock in pl'ace. The hand knob 20 is turned to press the sleeve 17 against thecenter 16, and the sleeve is locked in adjristed position by means of the clamp 17a.

he clutch 49 being in the thrown-out position, the shaft 45 is rotated manually until the side of the forward end if the thread is near the working portion of the grinding wheel B, after which the clutch 49 is thrown in. The handle 88 the wheel B toward the hob. The flange 59 is then adjusted with relation to the ring `60 until the hob is in proper relation to the cam 71. The machine is then set in operation, whereby the wheel B is rapidly rotated, the slide 1 slowly advanced, and the spindle 9 slowly rotated. By means of the shaft 41 the operator accelerates the feed movement of the slide 1 until the grinding wheel is making a proper cut. After the hob has been fed past the grinding wheel B the machine is stopped, said Wheel is Withdrawn by operating the handle 8 and the slide 1 is returned to initial position by reversing the .drive for the pulley 29. After the slide has been returned to initial position, the machine is stopped, the wheel B is returned to working position by means of the liand-lever 88, and the achine again set in operation to feed tlli hob pastthe grinding wheel. The operator turns, the shaft 41 so as to advance the slide 1 sufficiently to enable the wheel B to make a second cut of proper depth.

After one side of the thread has been completely ground, the machine is stopped, the clutch 49thrown out, the wheel B retracted by means of the lever 88,. the slide 1 returnedby means of the shaft 45, `and the clutch 49 thrown in. The screw 98 (Fig. l5) is withdrawn; the detent pin 108 is removed from the notch 107 with which it is in engagement;.the fiame 93 is frame '93 rigidly in place. The belt 129 is then reimate position to be ground. The machine is started upV and the shaft 41 is turned until the wheel is making a proper cut. After the second side of the thread has been made smoothpthe operator employs at intervals a gage in order to ascertain when the has been completely ground. The form of gage herein shown comprises a gage member 130 (Figs. l and) mounted for sliding movement toward and away from the hob in a carrier 131, said carrier being slidable longitudinally of the hob on a guide bar 132. The bar 132 is remgvably and stationarily supported upon two posts 133 on the slidel. The gaging is, of course, done when the machine is idle.

Ingrinding a multiple-thread hob the spindle 9 is indexed or tu-rned with relation the gear wheel 26 after each thread has been completely ground. A suitable gage (not shown) would be applied by the operator to determine when' the grinding of a thread has been completed.

Suitable modifications are made in the change-gear train 54, 55, 56 in accordance with changes in the number of threads of the hob.

As shown, the machine is arranged to grind a right-hand hob. To operate upon a left-hand hob an additional change gear (not shown) would be provided in the gear train 54, 55, 56 so as to reverse the direction of feed movement of the slide 1. f

Changes in'the gear train 74,75 and 76 are made as required by the number of utes or gashes in the hob to be ground, and when changing from a hob having straight flutes to one having spiral iutes or vice versa. Variations` in the amount of relief of the teeth of the hobs operated upon are taken care of by changes in the shape of the cam 71.

A decrease in the diameter of the wheel B, due to wear and dressing, is adjusted for by advancingthe slide 82 with relation to the slide 69 byturning the screw 85, and by retracting the head 111 by adjusting the nuts 117.

I claim as my invention:

The method of grinding a hob having a. spiral series of relieved teeth which includes the steps of positioning a grinding wheel cause the latter to assume a position 180 y l i `removed from the first position, the axis on which such reversal occurs being perpendicular to the axis of the hob and parallel to the plane of reciprocation, said axis of reversal intersecting the line of contact be-g tween the grinding Wheel and the hob at the the Wheel and the hob to e'ect the grinding pitch line of the hob; moving the hob aX- of the other side of each of said relieved ally approximately one half` the circular teeth. 10 pitch of the hob to bring the other side of In testimony whereof, I have hereunto at- 5 the spiral series of teeth into position to be Aiixed my signature.

ground; and rotating the Whee1` and the hob and effecting relative reciprocation between JOHN EDGAR. 

